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Precision photometric calibration is key to a number of astrophysical research areas such as supernova cosmology and dark energy studies. In the age of large surveys, pushing the limits of photometry is a worthy challenge, with traditional…
The optical observations of wide fields of view encounter the problem of selection of best exposure time. As there are usually plenty of objects observed simultaneously, the quality of photometry of the brightest ones is always better than…
A particle tracking velocimetry apparatus is presented that is capable of measuring three-dimensional particle trajectories across large volumes, of the order of several meters, during natural snowfall events. Field experiments, aimed at…
The PAU (Physics of the Accelerating Universe) Survey goal is to obtain photometric redshifts (photo-z) and Spectral Energy Distribution (SED) of astronomical objects with a resolution roughly one order of magnitude better than current…
The sky photon background flux has been measured at the southern Auger site in Malargue, Argentina, using the observatory's fluorescence detectors (FD). The analysis is based on ADC variances of pixels not triggered by the First Level…
We have built an Atmospheric Transmission Monitoring Camera (aTmCam), which consists of four telescopes and detectors each with a narrow-band filter that monitors the brightness of suitable standard stars. Each narrowband filter is selected…
The simple physics of microlensing provides a well-understood tool with which to probe the atmospheres of distant stars in the Galaxy and Local Group with high magnification and resolution. Recent results in measuring stellar surface…
Optical interferometry has been successful at achieving milliarcsecond resolution on bright stars. Imaging performance can improve greatly by increasing the number of baselines, which has motivated proposals to build large (~ 100 m) optical…
We present a method to estimate distances to stars with spectroscopically derived stellar parameters. The technique is a Bayesian approach with likelihood estimated via comparison of measured parameters to a grid of stellar isochrones, and…
The southern Pierre Auger Observatory, presently under construction in Malarg"ue, Argentina, is nearing completion. The instrument is designed to measure extensive air-showers with energies ranging from $10^{18}$-$10^{20}$ eV and beyond. It…
The presence of clouds between an airshower and a space-based detector can dramatically alter the measured signal characteristics due to absorption and scattering of the photonic signals. Furthermore, knowledge of the cloud cover in the…
We show the astrometric potential of the Wide Field Imager at the focus of the MPI-ESO 2.2m Telescope. Currently, we are able to measure the position of a well-exposed star with a precision of $\sim$4 mas/frame in each coordinate (under 0.8…
The techniques of laser cooling combined with atom interferometry make possible the realization of very sensitive and accurate inertial sensors like gyroscopes or accelerometers. Besides earth-based developments, the use of these techniques…
An optimal maximum-likelihood technique for computing point-source image centroids from many, slightly offset, CCD frames is presented. The method is especially useful for measuring stellar proper motions from data taken with the Wide Field…
Spherical harmonic moments are well-suited for capturing anisotropy at any scale in the flux of cosmic rays. An unambiguous measurement of the full set of spherical harmonic coefficients requires full-sky coverage. This can be achieved by…
Astronomers working with faint targets will benefit greatly from improved image quality on current and planned ground-based telescopes. At present, most adaptive optic systems are targeted at the highest resolution with bright guide stars.…
ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) mission concept is to conduct high-precision measurement of relativistic effects,solar-system parameters and gravitational waves. In this paper, we first extend the…
During 2003, a camera designed to measure the optical pulsations of pulsars was installed on a telescope of the H.E.S.S. array. The array is designed for gamma-ray astronomy in the ~100 GeV - 100 TeV energy regime. The aims of this exercise…
The strength and vertical distribution of atmospheric turbulence is a key factor determining the performance of optical and infrared telescopes, with and without adaptive optics. Yet, this remains challenging to measure. We describe a new…
This paper summarizes the status and the recent measurements from the Pierre Auger Observatory. The energy spectrum is described and its features discussed. We report searches for anisotropy of cosmic ray arrival directions on large scales…